Sorghum genetic variation in calcium (⁴⁵Ca) uptake

Abstract

Sorghum [Sorghum bicolor (L.) Moench] seedling root tips (1 cm) were sequentially immersed in 10 mM EDTA to remove mucigel, p‐chloromercuribenzene sulfonic acid (PCMBS) (0 and 10 mM) (1 hr), pH 6.0, 5.5, 5.0, 4.5, or 4.0 solutions (0.1 μCi ⁴⁵Ca) as maintained by 0.01M NaAc buffer, and 10 mM EDTA (10 min). PCMBS untreated root ⁴⁵Ca uptake decreased as the external solution pH dropped below pH 6.0 in SC574 and SC283 to minimums at pH 5.5 in SC574 and pH 5.0 in SC283. In Funk G522DR, PCMBS untreated root ⁴⁵Ca uptake increased as pH decreased from pH 6.0 to pH 5.0 and ⁴⁵Ca uptake decreased at lower pH's. Ion channel mediated ⁴⁵Ca uptake (+ 10 mM PCMBS) accounted for ‐90% of the ion uptake in SC574 at pH 6.0, 78% of the total ⁴⁵Ca absorbed at pH 6.0 in SC283, and 65% of the ⁴⁵Ca absorbed at pH 6 in Funk G522DR. Decreased external pH induced decreased ⁴⁵Ca absorption in PCMBS treated roots in all three cultivars with different patterns of maximum and minimum ⁴⁵Ca uptake.